Version(s): 10
A cased opening can be created by drawing any opening on the wall. Then Edit > Edit Item and select the opening.
Change the opening Type to a Solid Arch with the desired style. In the Options menu, select the Interior Trim
option.

Version(s): 11 +
A cased opening can be created by drawing an Arch opening (Draw > Opening > Arch) of the desired shape. Then
the opening can be edited (Edit> Edit Item). Select the Trim tab and place a check beside Interior Trim.